Compressible material folding shoe

ABSTRACT

A method and apparatus for processing compressible insulation material of mineral fibers in which a folding shoe guides the insulation material from a strip condition into a cylindrical condition and further including initially compressing the portion of the strip material along the centerline thereof, subsequently compressing the portions of the strip material intermediate the center line and the side edges of the strip material, and, finally, compressing the side edge portions of the strip material.

TECHNICAL FIELD

This invention pertains to handling compressible strip material, such asfibrous mineral insulation material. In one of its more specificaspects, this invention relates to guiding compressible fibrous materialcontaining a heat-hardenable binder into a cylindrical shape andcompressing the material to prepare it for subsequent heating to curethe binder.

BACKGROUND OF THE INVENTION

A common method for forming cylindrical products from fibrous material,such as pipe insulation, is to helically wind rectangular strips offibrous material on a mandrel, and place the mandrel within a mold wherethe material is heated and compressed to cure the binder on the fibers,thereby forming a cylindrical insulation product. A variation of thismethod is a batch process in which the fibrous material is clampedbetween two mold halves and then heated and compressed. Helical windingand batch processes are slow and require large amounts of capital andlabor. Another process for producing cylindrical insulation products isa continuous molding process in which a strip of fibrous material isfolded to a cylindrical shape and fed through a cylindrical mold whichcompresses and/or heats the material to cure it, thereby continuouslyproducing a substantially rigid insulation product. A guide shoe isordinarily used to continuously fold the flat strip of insulationmaterial so that the side edges join to form the strip into acylindrical shape. The guide shoes also compress the material prior toits advancement into the curing apparatus. Continuous molding processesof the prior art generally use axially symmetric folding shoes, such asconical or parabolic shoes, to form and compress the strips intocylindrical shape.

One of the problems associated with the continuous insulationmanufacturing processes of the prior art is that the portion of theproduct near the seam created where the sides of the strip material areadjoined, usually at the top of the cylindrical insulation piece, isstructurally weak. Advantageously, the edges of the strip material willbe bonded together so that the seam is neither visually nor structurallyevident. In practice, however, the seams of pipe insulation made by thedevices of the prior art are weak, and subsequent fabricationoperations, such as slitting pipe insulation pieces for packaging, oftenresult in defective products due to separation at the seam. Anotherproblem associated with the continuous molding of pipe insulationmaterial is that the forces placed on the strip material passing throughthe folding shoe are sometimes so great that breakage or unacceptablefolding of the strip material occurs. The use of axially symmetricfolding shoes contributes to undue tension in the strip material. Theapparatus and method of this invention are directed towards solution ofthe above problems.

SUMMARY OF THE INVENTION

According to this invention, there is provided a method for guidingcompressible strip material into a cylindrical shape of the type inwhich the strip material is passed lengthwise through a folding shoe,the portion of the strip material along the centerline of the stripmaterial is compressed, the portions of the strip material intermediatethe centerline and the side edges of the strip material are compressed,and the side edge portions of the strip material are compressed.

In a specific embodiment of the invention, the strip material is causedto migrate in the direction from the centerline to the side edges as thestrip material passes through the folding shoe.

According to this invention, there is also provided a method forprocessing compressible insulation material of mineral fibers of thetype in which the insulation material is passed through a folding shoewhich guides the insulation material from a flat condition to a shapehaving a generally circular cross section, the insulation material isfolded around a cylindrical mandrel positioned within the folding shoeand the insulation material at the bottom of the mandrel is compressed,the portions of insulation material at the sides of the mandrel aresubsequently compressed, thereby causing some of the insulation materialto migrate upwardly toward a position above the mandrel, and, finally,the insulation material at the top of the mandrel is compressed. It hasbeen found that the progressive compression of the insulation materialfrom the centerline of the strip to the edges of the strip, or from thebottom of the mandrel to the top of the mandrel, results in a higherconcentration of insulation material and binder in the area of the seam.The greater concentration of insulation in the seam area results in astronger and more preferable insulation product.

In a specific embodiment of the invention, the insulation material ispulled through the folding shoe with a web material.

According to this invention, there is also provided a fibrous mineralpipe insulation product made according to the method of the invention.

According to this invention, there is also provided a pipe insulationproduct of the type formed from a flat strip of fibrous mineralinsulation material folded into a cylindrical shape and joined bycompression at the seam, where the portion of the product nearest theseam has a density within the range of from about 10 percent to about 30percent, by weight, greater than that of the remaining portions of theinsulation product.

In a specific embodiment of the invention, the portion of the productnearest the seam has a density of about 20 percent greater than that ofthe remaining portions of the product.

According to this invention, there is also provided apparatus forguiding compressible strip material into a cylindrical shape of the typein which the strip material is passed lengthwise through a folding shoe,where the inlet portion of the folding shoe is adapted to compress theportion of the strip material along the centerline of the stripmaterial, the intermediate portion of the folding shoe is adapted tocompress the portions of the strip material intermediate the centerlineand the side edges of the strip material, and the outlet portion of thefolding shoe is adapted to compress the side edge portions of the stripmaterial.

In a specific embodiment of the invention, the intermediate portion ofthe folding shoe is adapted to cause the strip material to migrate inthe direction from the centerline to the side edges.

In a preferred embodiment of the invention, means for driving a webmaterial to pull the strip material through the folding shoe isprovided.

According to this invention, there is also provided apparatus forprocessing compressible insulation material of mineral fibers of thetype in which the insulation material is passed lengthwise through afolding shoe, positioned in which is a cylindrical mandrel, where theoutlet portion of the folding shoe is adapted to fold the insulationmaterial around the mandrel and adapted to compress the insulationmaterial at the bottom of the mandrel, the intermediate portion of thefolding shoe is adapted to compress the portions of the insulationmaterial at the sides of the mandrel and to cause some of the insulationmaterial at the sides of the mandrel to migrate upwardly toward aposition above the mandrel, and the outlet portion of the folding shoeis adapted to compress the insulation material at the top of themandrel.

In a specific embodiment of the invention, the cross section of theinlet portion of the folding shoe in an ellipse.

In another embodiment of the invention, the ellipse has a horizontalmajor axis.

In a preferred embodiment of the invention, the center of the ellipse ispositioned above the center of the mandrel.

In another preferred embodiment of the invention, the horizontal axis ofthe ellipse becomes shorter from the inlet portion of the folding shoeto the intermediate portion, and the vertical axis of the ellipsebecomes shorter from the intermediate portion to the outlet portion.

In the most preferred embodiment of the invention, the folding shoe hasthe shape of an elliptical cycloid.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of a portion of a strip of insulationmaterial.

FIG. 2 is a schematic view in elevation of the apparatus for formingcylindrical products from the strips of insulation material according tothe principles of the invention.

FIG. 3 is a schematic plan view of the apparatus of FIG. 2.

FIGS 4, 5 and 6 illustrate views of the apparatus taken along lines4--4, 5--5 and 6--6, respectively, of FIG. 2.

FIG. 7 is a perspective view of the two halves of a folding shoeaccording to the principles of the invention.

FIG. 8 is an end perspective view of the folding shoe of FIG. 7.

DESCRIPTION OF THE INVENTION

As shown in FIG. 2, the insulation strip material 10 is advanced throughfolding shoe 12 where it is folded into a cylindrical shape andcompressed prior to being advanced to die 14. As the material isadvanced through the die, it is heated to a temperature sufficient tocure the binder on the insulation material. The use of such dies is wellknown in the prior art. Emanating from the die us the cured cylindricalpipe insulation product 16. Positioned within the folding shoe and dieis mandrel 18, which together with die bore 20 defines a die openinghaving an annular cross section. The apparatus can be adapted with webmaterial 22 and web take-up reel 24 to assist in pulling the insulationmaterial through the folding shoe and the die in the manner well knownin the art.

As shown in FIG. 1, the strip insulation material can be divided intothree portions, center portion 26 adjacent centerline 28, side edgeportions 30 adjacent side edges 32, and intermediate portions 34 whichis intermediate the center portion and the side edge portions.

In order to provide the desired compression of the folded insulationmaterial, the folding shoe is comprised of three portions, eachproviding compression for a different part of the insulation material.As shown in FIGS. 3 and 7, the folding shoe is comprised of inletportion 36, intermediate portion 38 and outlet portion 40. For ease ofconstruction and handling, the folding shoe can be formed in two halves,as shown in FIG. 7.

As shown in FIGS. 4 through 6, when the insulation material is foldedaround the mandrel into a cylindrical shape, the center portion of theinsulation is positioned at the bottom of the mandrel, the intermediateportions of the insulation are positioned at the sides of the mandreland the side edge portions of the insulation are positioned at the topof the mandrel. As shown in the cross-sectional view in FIG. 4, thecenter portion of the insulation material, which is at the bottom of themandrel, is compressed.

As the insulation material is advanced from the inlet portion of thefolding shoe to the intermediate portion of the folding shoe, theintermediate portions of the insulation material at the sides of themandrel are compressed, as shown in FIG. 5. Because of the compressionat the sides of the mandrel, the insulation material has a tendency tomigrate upwardly in a direction from the centerline of the insulationmaterial toward the side edges of the insulation material. This has theeffect of concentrating more of the insulation material above the top ofthe mandrel.

As the insulation material is advanced to the outlet portion of thefolding shoe, the side edge portions of the insulation material at thetop of the mandrel are joined and compressed, as shown in FIG. 6. Seam50 is formed by the joining of the two side edges of the insulationmaterial. As indicated by FIGS. 4, 5 and 6, the resulting insulationproduct has a higher density at the portion nearest the seam. Thedensity of the portion nearest the seam, which is the side edge portionof the insulation material, can be within the range from about 10percent to about 30 percent, by weight, greater than the density of thecenter and intermediate portions of the insulation material. In thepreferred embodiment, the side edge portion of the insulation materialhas a density of about 20 percent greater than that of the remainingportions of the product.

As can be seen from FIG. 4, the cross section of the inlet portion ofthe folding shoe can be an ellipse having horizontal major axis 42 andvertical minor axis 44. Also, center 46 of the ellipse can be positionedabove center 48 of the mandrel. As shown in FIG. 5, the horizontal axisof the ellipse becomes shortened as the insulation material is advancedfrom the inlet portion to the intermediate portion of the folding shoe.The vertical axis of the ellipse is shortened as the insulation materialis advanced from the intermediate portion to the outlet portion of thefolding shoe, as shown in FIG. 6. In the best mode of the invention, thefolding shoe is in the shape of an elliptic cycloid, represented by thefollowing equations: ##EQU1## where x is the distance from the entranceto the die, a(x) is one half the vertical axis of the folding shoe crosssection, b(x) is one-half the horizontal axis of the folding shoe crosssection, 1_(a) is the length of the inlet portion of the folding shoe,1_(b) is the length of the outlet portion of the folding shoe, and L isthe length of the folding shoe.

Although the cross section of the inlet portion of the folding shoe isshown as being elliptical in shape, it is to be understood that othergeometric configurations can be used to provide the gradual compressionand concentration of the insulation material according to the principlesof the invention. Also, the principles of this invention will apply toproducts having non-circular cross sections.

EXPLOITATION IN INDUSTRY

This invention will be found to be useful in the manufacture of pipeinsulation products, such as pipe insulation made from glass fibers.

We claim: .[.1. In a method for guiding compressible strip material intoa cylindrical shape of the type in which the strip material is passedlengthwise through a folding shoe and wrapped around a mandrelpositioned within said folding shoe, the improvement comprising: andbottom of the mandrel..].
 8. .[.The apparatus of claim 7 in which.]..Iadd.In apparatus for processing compressible insulation material ofmineral fibers of the type in which the insulation material is passedlengthwise through a folding shoe, positioned in which is a cylindricalmandrel, the improvement comprising:the inlet portion of said foldingshoe being adapted to fold the insulation material around said mandreland to compress the insulation material at the bottom of said mandrel;the intermediate portion of said folding shoe being adapted to compressthe portions of the insulation material at the sides of said mandrel andto cause some of the insulation material at the sides of the mandrel tomigrate upwardly toward a position above said mandrel resulting in aheavier concentration of the strip material above the top of themandrel; the outlet portion of said folding shoe being adapted tocompress the insulation material at the top of said mandrel so that thedensity of the insulation material at the top of the mandrel is greaterthan at the sides and bottom of the mandrel; and .Iaddend.the crosssection of said inlet portion .[.is.]. .Iadd.being .Iaddend.an ellipse.9. The apparatus of claim 8 in which said ellipse has a horizontal majoraxis.
 10. The apparatus of claim 9 in which the center of said ellipseis positioned above the center of said mandrel.
 11. The apparatus ofclaim 10 in which the horizontal axis of the ellipse becomes shorterfrom said inlet portion of said folding shoe to said intermediateportion of said folding shoe, and in which the vertical axis of theellipse becomes shorter from said intermediate portion of said foldingshoe to said outlet portion of said folding shoe. .Iadd.12. Theapparatus of claim 8 in which said folding shoe has the shape of acycloid. .Iaddend.